Getting Ready for Big Cut Number 1

With a bit of Wintery weather moving in this week it was time to put some thought into the next steps for the LE mod. I disassembled the 2 408 ribs and the subskin from the LE and deburred the new holes. Then I used the file to remove a bit more material from the flanges on the modified 408 rib. THis is necessary not only for the clearance of the shop head of the rivet that goes into the last hole on both flanges, but also needs to clear the dimples that will get created in the subskin and the outer LE skin.

I also measured and marked the center lines on both rear rib flange extensions to check for rivet edge distance clearance. Only one rivet hole will drilled in each of these pieces, but before I do that I need to attach each one to the rib web (6 AN470 rivets each). Before I can do THAT I need to prime that entire rib. So it looks like some priming will be in order once the temps climb back up to above 55 degrees.

In the mean time I started drawing up the plans for making the necessary cuts to the subskin. I needed to use the 12 inch x 36.5 inch piece of .032 aluminum so I could make the correct bend to achieve the contour of the leading edge curve. However, since the subskin is basically nothing more than a mounting platform for the outer skin section that will slip over it, I don;t need to keep all of that metal on the subskin.

The big question now is how far to trim the subskin metal on both sides. I am currently evaluating exactly where I need to make the critical cuts in the subskin, and I pretty much have to get this right the first time. There is a lot to consider here, including stress points along the curvature of the leading edge, how many screw attach points and nut plates to use, and where each of them should be located. If I screw that up then I will get to start all over again, and may very likely also need to order  a brand new LE skin and  ribs, due to the potential to oversize the holes in the outer skin by having to re-drill through them several more times.

So needless to say I need to thoroughly think this through and very clearly understand exactly where to trim the metal on the top and bottom sides of the subskin, prior to trimming any of it away. As usual, pics showing how I am doing this will be more clear than describing it. The best way to describe it is that this is a bit of a multi-layered jigsaw puzzle, with an oddly shaped curve in the middle, where the inner and  outer layers need to be trimmed very precisely, and the pieces are on the top and also on the bottom. Its a bit more complicated than your garden variety square access panel in a piece of flat aluminum, but the concepts are still the same.

KPR.